Why there is some missing content in c#

Question

I learn computer science in high school and in my spare time I use solo learn. And I noticed that there are some things that I can't learn in solo learn like randoms and there are another things that I can't remember right now. Why is that?

Answer 1

Sololearn is aimed towards complete beginners and the courses only scratch on the surface for that reason.

Answer 2

there is a lot of think havent been covered here because this app learns the concepts only.
but if you needed more then go to MSDN or good books like fundmental of c#.

Answer 3

Than there is a way to learn more in depth? An app of some kind?